Electrical submersible pumps (ESP) are often used to pump fluids from hydrocarbon wells. An ESP includes a motor, a pump, and a seal section that reduces a pressure differential between well fluid on the exterior and dielectric lubricant in the motor interior. An ESP may have other components, such as a gas separator or additional pumps, seal sections and motors in tandem.
A power cable extends from the surface to the motor for supplying three-phase power. Usually, the power cable has three conductors, each of which is separately insulated. A single elastomeric jacket is extruded over the three insulated conductors. A metal strip or armor wraps around the jacket. In round cable, the exterior of the jacket is cylindrical in cross-section. In some installations, a tube extends alongside the armor of the power cable. The tube may be used to convey liquids, or the tube may have an instrument wire located inside. It is known to wrap the tube and the armor together with another metal strip.
In most cases, a string of production tubing supports the ESP, and bands secure the power cable to and alongside the production tubing. When the ESP has to be retrieved for repair or replacement, a workover rig is required to pull the tubing along with the power cable and ESP.
It is desirable to avoid having to employ a workover rig to retrieve the ESP. However, a conventional power cable cannot support its own weight in many wells, thus needs additional support. One technique involves placing the power cable within coiled tubing, which is a continuous length of metal tubing deployed from a reel. The pump discharges up an annular space surrounding the coiled tubing.
Various methods have been proposed and employed to transfer the weight of the power cable to the coiled tubing. In one method, the power cable with armor is pulled through the coiled tubing after the coiled tubing has been formed. Various standoffs or dimples formed in the coiled tubing engage the armor to anchor the power cable within the coiled tubing. In another method, the power cable without an armor is placed in the coiled tubing as the coiled tubing is being formed and seam welded.